void account_book(){
    FILE *book;
    book = fopen("book.txt","a+");
    long long int chiwhan_for_ISBN;
    int chiwhan_for_book_num;
    char answer;
        book_node *newnode = (book_node *)malloc(sizeof(book_node));
        book_node *tmp = head_book;
        system("clear");
    printf(">> 도서 등록<<\n");
    getchar();
    printf("도서명:");
    scanf("%[^\n]",newnode->book_name);
    getchar();
    printf("출판사:");
    scanf("%[^\n]",newnode->book_publisher);
    getchar();
    printf("저자명:");
    scanf("%[^\n]",newnode->book_writer);
    getchar();
    printf("ISBN:");
    scanf("%lld",&(newnode->ISBN));
    getchar();
    printf("소장처:");
    scanf("%[^\n]",newnode->locate_place);
    getchar();
   newnode->yes_or_no = 'Y';
    /*printf("\n자동입력 사항\n\n");
    printf("%lld",newnode->ISBN);
    */
 while (1) {
        if(tmp == NULL){
            head_book = newnode;
            tmp = head_book;
            break;
        }
        if (tmp->next == NULL){
            newnode->book_num = (tmp->book_num)+1;
            tmp->next = newnode;
            break;
        }
            tmp = tmp->next;
    }
    printf("대여가능 여부: Y\n");
    printf("도서번호 %d\n\n",newnode->book_num);
    printf("등록하시겠습니까?");
    scanf("%c",&answer);
    getchar();
    if(answer == 'Y' || answer == 'y')
      book_restore();
    else if(answer == 'N' || answer == 'n'){
        if(tmp->next ==NULL)
            tmp = NULL;
        else
            tmp->next == NULL;
    }
}